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Solution «Prilling by Vibration Wet» (150 – 2000 μm)

Formation of beads and capsules of various materials

You wish to encapsulate various materials into a polymeric matrix. We offer the creative solution using vibrating technology (prilling) to form beads and capsules, even with extremely sensitive and expensive materials.

Concentric nozzle set

Set of 8 single nozzles

Set of 8 single nozzles with high precision opening of 0.08, 0.12, 0.15, 0.20, 0.30, 0.45, 0.75 and 1.00 mm, made of stainless steel including nozzle rack.

Reaction vessel for sterile apllications

Completely autoclavable reaction vessel made of glass and stainless steel for the sterile production and collection of microcapsules, 2 litre working volume; incl. bead producing unit and set of 8 single nozzles.

The most important parameter for capsule production is the size of the shell nozzle. In general final capsule diameter is about twice the size of the shell nozzle aperture.
What influences the core size within core-shell capsules.

The most important parameter for core size within capsules is the size of the core nozzle and the flow rate of the core material. In general final core diameter within capsules is about 1-2.5 times the size of the core nozzle aperture with increasing with increasing flow rates resulting in larger diameters.

Is scale up of the process possible and how can it be achieved?

Scale up is simply done by multiplying the number of nozzles on the machine, and is referred to as the multi-nozzle system. The parameters used for the one nozzle system should also apply to the multi-nozzle system. Therefore a special scale-up development is not required. However the process must work and be stable when using the one nozzle system before switching to a multi-nozzle system: Buchi offers such a multi-nozzle system which enables between 1 and 6 nozzles to be operated simultaneously by the operator.

What is the optimal frequency and amplitude range to work within for different nozzle size?

What type of alginate should be used?

Alginate is a natural polymer deviated from the cell wall of various different seaweed plants. On account of its natural origin the type of alginate supplied by different suppliers can vary extensively and this variable composition can have a negative effect on the quality of the alginate. This can result in the production of low quality particles or in some cases beads/capsules cannot be produced, while it also affects reproducibility of experiments.
Buchi now supplies high quality alginate with a consistent composition. Each batch of alginate is pre-tested by scientists at Buchi to ensure customers can consistently produce high quality beads/capsules in a reproducible manner.

Polymer solution cannot be pumped through the nozzle and bead producing unit. What can I do?

In this case either the nozzle or the bead producing unit is blocked with dried polymer.
Cleaning nozzle: See nozzle cleaning section

Cleaning bead production unit: If alginate is being used, soak the unit in 0.1 M NaOH for 1 hour and then pump the NaOH through the unit using a syringe pump or place the unit within a sonication bath for 1 – 5 minutes to loosen the alginate. For gelatin either soak in hot water (> 60 °C) and flush or sonication as above.

For most materials, sonication will help to unblock it and the unit should be flushed with a liquid with can dissolve the entrapped material i.e. for PGLA this can be dichloromethane.

Blocking of the pre-filter in the producing unit can also prevent the pumping of the polymer material through the bead producing unit and should be changed. See YouTube videos for more details.